Integrated biorefinery development for the extraction of value-added components and bacterial cellulose production from orange peel waste streams

An integrated biorefinery has been developed using orange peel waste derived from catering services. Free sugars, essential oils and a phenolic-rich extract were initially separated from the orange peels. Liquid chromatography–mass spectrometry analysis showed that the phenolic-rich extract contained mainly quinic acid followed by hesperidin and hesperetin. Pectin was extracted from the remaining orange peel residues via dilute HCl or citric acid treatment followed by pectin precipitation with ethanol leading to pectin-rich extracts with pectin purity up to 54% (w/w). Process design showed that 62% lower energy consumption could be achieved in the pectin separation process when the pectin-rich liquid extract derived via HCl treatment is concentrated at 25% of the original volume prior to pectin precipitation via ethanol treatment. The pectin-free solid residue was subjected to hemicellulose (72.5%) and cellulose (70.4%) hydrolysis via sequential diluted H2SO4 pretreatment and enzymatic hydrolysis. Sugars derived from orange peels were used in Komagataeibacter sucrofermentans cultures in tray bioreactors under air sparging leading to 11.6 g/L bacterial cellulose concentration with productivity of 1.55 g/L/day. The proposed biorefinery led to the production of 1.5 kg essential oils, 1.3 kg phenolic-rich extract, 34 kg pectin-rich extract and 68 kg bacterial cellulose from 1 t of orange peel waste.